Hoist drawbar



June 1950 c. D. WOODWARD ETAL 2,513,224

HOIST DRAWBAR Filed Sept. 17, 1947 FIGJ INVENTORS CLIFFORD D. WOODWARD MARCUS M CANNA QW M m/ ATTO R N EYS Patented June 27, 1950 HOIST DRAWBAR Clifford D. Woodward and Marcus McCanna, Butte, Mont., assignors to Anaconda Copper Mining Company, Ne

tion of Montana w York, N. Y., a corpora- Application September 1'7, 1947, Serial No. 774,594

7 Claims. (Cl. 187-81) This invention relates to drawbars for lifts or hoists, and provides an improved drawbar especially adapted for use on mine hoists. The drawbar of a hoist is the device by which the hoist cable is connected to the transverse yoke of the hoist car frame. In mine hoist terminology, the car is usually called a cage (if for carrying people), or a skip (if for carrying freight). The term ski-p has been chosen for use in this specification, but with the intention of including mine hoist cages, or even ordinary elevator cars, within the scope of it meaning.

It is evident that the drawbar must carry the full load of the skip and its load, and must provi-de for making a secure connection between the cable and the yoke. Strong, soundly designed and well made drawbars are therefore imperative to guard against accidents which can result in dropping of the skip through the great vertical distances of mine shafts. Indeed, accidents resulting in loss of life have occurred through failure of mine hoist drawbars.

The present invention provides a simple and readily made drawbar, but one that can be made to possess adequate strength for supporting even the heaviest skip loads. The new drawbar, moreover, is designed to cooperate with simple but rugged safety dogs for checking and stopping descent of the skip in the event of failure of the hoist cable.

The new drawbar comprises an assembly of laminae. Each lamina is in the form of a narrow elongated hook, and they are arranged alternately right-hand and left-hand so that the assembled drawbar made therefrom has a narrow transverse slot for receiving the yoke of the hoist skip, a solid base, a paled body, and a solid upper portion. The upper portion is configured to form an eyelet for attachment to the hoist cable. Bolts extending through both the solid base and the solid upper portion fasten the laminae securely together. Drawbars thus made in accordance with the invention can be fabricated easily with ordinary machine-shop equipment from plate stock of high tensile strength, and the drawbar may be so designed as to possess an extremely favorable stress pattern. Moreover, it can be assembled in position about the hoist yokea feature of considerable importance in 'cases where the yoke design is such that neither end can be slipped through a properly dimensioned drawbar slot.

The transverse slot of the new drawbar, in which the yoke is received, preferably is 9f substantially greater height than the yoke itself.

Thus the drawbar is capable of vertical movement, between upper and lower limits, relative to the yoke. This feature is of advantage for use in connecting the drawbar to safety dogs by which the skip may be stopped in its descent in the event of a cable failure.

Preferably the skip of any mine hoist using the new drawbar includes a pair of rotatable safety dog shafts arranged on opposite sides of the yoke and carrying safety dogs so mounted that they may be quickly brought, by rotation of the safety dog shafts, into gripping engagement with the guide rails by which the skip is guided in the mine shaft. Springs normally urge such rotation of the safety dog shafts. The dogs, however, are normally held in their retracted position, against the force of the springs, out of engagement with the guide rails, by ropes connected to the drawbar and, through levers, to the safety 'dog shafts. When the drawbar is held by the hoist cable at its upper limit of movement relative to the yoke, the safety dogs are held in their retracted position, out of engagement with the guide rails, by the torque, exerted by the ropes through the levers, on the safety dog shafts. In the event of a cable failure, however, the drawbar may be drawn to its lower limit of movement relative to the yoke by the springs, which at the same time rotate the safety dogs into gripping engagement with the guide rails. Thus, with the new drawbar, the skip may be stopped quickly and automatically in the event of a cable failure;

A preferred embodiment of the invention, embodying the foregoing and other features, is described below with reference to the accompanying drawings, in which Fig. 1 is a schematic section through a mine shaft showin the relation of the new drawbar to the hoist skip and cable;

Fig. 2 is a side view of the new drawbar as it appears connected to the yoke of the hoist skip, and showing one of the safety dogs by which the skip is stopped in the event of a cable failure;

Fig. 3 is a horizontal section taken substantially along the line 33 of Fig. 2;

Fig. 4 is a vertical section taken substantially along the line 4-4 of Fig. 2;

Fig. 5 is a view looking in the direction 5-5 of Fig. 2, but showing the drawbar in the position in which the safety dogs are permitted to engage the guide rails; and

Fig. 6 is a fragmentary section of the base of the new drawbar taken substantially along the line 66 of Fig. 6.

to this center line.

upper laminae: portions 20.

Fig. 1 illustrates schematically a mine hoist comprising a skip Ill suspended in a mine shaft H :by a cable I? from a head-frame installation 13. The ski-p is guided in its travel in the mine shaft by guide rails It. A yoke [5, which is a transverse element of the skip frame, is connected to the cable l2 by a. drawbar [6 constructedin accordance with the invention.

The drawbar It is shown on an enlarged scale in Figs. 2 to 6, together with safety apparatus by which a free fall of the skip may be checked and stopped in the event of a, failure such as breakage of the cable 12.

Referring particularly to Figs. 2 and 4, it is seen that the drawbar is made up of a considerable number of laminae HR, and UL. Each lamina is in the form of a narrow elongated hook having a lower transverse portion l8, an intermediate vertical portion l9, and an upper vertical portion 20. The lower transverse portion 18 and the upper vertical portion 20 of each lamina is substantially symmetrical about a common vertical center line (Fig. 1), but the intermediate vertical portion 59 of each lamina is offset-laterally with respect The formof all of the laminae HR andllListhe same, but the laminae are assembled alternately right-hand and lefthand (reference numeral l'I-R denotes-the laminae assembled right-hand as viewed in Fig. 4, and referencenumeral I TL denote-s'the laminae assembl'ed left-hand as viewed in Fig. 4). The assembly of laminae, arranged alternately righthand and left-hand, forms a drawbar having a solid base composed of the contacting lower laminae portions l8, a paled' body composed of the spaced intermediate laminae portions H3 and a solidupper section composed of the contacting A transverse slot 2|, defined by the facing inner edges of the offset intermediate laminae portions l9, receives the yoke I5 of the hoist skip.

The assembled laminae are firmly bound together by a pair of transverse bolts 22 extending through aligned holes in the lower laminae portions I8 forming the solid base of the drawbar, and by a third bolt 23 extending transversely through aligned holesin the upper laminae portions forming the solid upper section of the drawbar. The lower bolts 22 are arrangedon opposite sides of" the transverse slot 2!, and the upper bolt 23 is advantageously substantially on the vertical'center line of the assembled drawbar. Thus, when a load is imposed on the drawbar by the skip yoke l5, its solid lower portion forms a simple beam of great strength, and its paled body and solid upper portion are stressed almost solely in tension. Stress studies made on a. drawbar thus assembled, and in which the in- 'dividual laminae were carefully made with no wider than the central portion of the ycke itself- 4 2 is thick, and frequently the extremities or other off-center portions of the yoke are thicker than the central portion, or are permanently secured to the remainder of the skip frame, so that it is not possible to insert the yoke through the transverse slot of the drawbar unless the slot is undesirably wide, or without a great deal of work to detach the yoke from the skip frame.

In order to provide a good bearing surface for the yoke l5 against the solid base formed by the transverse lower portions [8 of the laminae, it is often desirable to mount a semi-cylindrical trans- Ve'rsebearing block 2''! on the drawbar base underlying the yoke l5. Threaded studs 28 may be welded to the extremities of the bearing block, to form therewith a U-bolt structure which may be fastened in place by nuts 29 drawn up against a clamping plate 30 which bears against the bottom surface of the drawbar base. The bearing block assembly is shown on an enlarged scale in Fig. 6.

It will'be noted'that the transverse slot 2! of the drawbar is of substantially greater vertical height than is the yoke l5 received in it. Thus the drawbar is capable of vertical movement relative to the yoke, between upper and lower limits determined by the difference in height between the slot 21 and the yoke [5. The drawbar is at its upper limit of such movement when drawn up in the position shown in Fig. 4, with the bottom of the yoke l5 resting on the drawbar base;

and itis at its'lower limit of such movement when the top edge of the yoke makes contact with the upper portion of the drawbar at the top of the slot Zl, as shown in Fig. 6. Movement of the drawbar relative to the yoke is constrained to a vertical path by guide strips 3| welded or otherwise secured to the side faces of the yoke adjacent the outermost laminae of the drawbar.

The provision for vertical movement of the drawbar relative to the yoke is for the purpose of actuating emergency stopping means to 'prevent a free fall of the skip in the event of an accident such as a break in the hoisting cable. The safety stopping mechanism, and the manner in which it is operatively connected to the drawbar, is shown in Figs. 2 to 5. The particular safety stopping mechanism shownin the drawings comprises a pair of transverse, rotatable safety dog shafts 32, arranged on opposite sides of the yoke l5 and securely journaled in bearings 33 that are rigidly and strongly mounted on the skip frame. A safety dog 34 is'keyed to each'end of each of these shafts, in position alongside the wooden guide rails I4 on which the skip travels. The safety dogs are formed with sharp teeth 35 located so that they may be brought, by rotation of the shafts 32, into gripping engagement with the guide rails l4. Strong torsion springs 35 are provided surrounding each safety dog shaft. One end of each of these torsion springs is anchored to the shaft it surrounds, and the other end is anchored to a housing 31 enclosing the spring and rigidly fastened to the skip frame. The springs are normally under substantial torsion, so as to urge rotation of the safety dog shafts 32 in the roper direction to bring the teeth 35 of the safety do s into gripping engagement with the hoist guide rails.

Also keyed to each safety dog shaft is a segmental pulley 38 which serves as a lever through which a torouemay be exerted on the safety dog shaft. opposite in direction to the torqu exerted thereon by the torsion springs 36; The segmental pulleys '38 are connected by short lengths of 7 are assembled alternately right-handxar'id lefthande the drawbar made therefrom thus having a transverse slot for receiving the yoke-of, the skip, a solid base for supporting said'yoke a paled body, and a solid upper portion, the transverse slot in said drawbar being of substantially greater height than the height of the yokeuit is designed toreceive.

5. A drawbar for a hoist having atransverse yoke, said drawbar comprising. a considerable i number of laminae each of which is tithe-form of anarrow elongated hook and which are assembled alternately right-hand and left-handito form a drawbar having a solid base,-a.-paled body,

a solid upper portion, and a transverseslotefon reception of the hoist yoke, the height .of, said slot being substantially greater than'the-height of said yoke so' thatv with the yoke received in the slot the drawbar may move a, substantial vertical distance between upper and lower limits relative to the yoke, the solid top of the drawbar being'formedwith an eyelet to which a cable may be attached, and atleast one of the right-hand and one of theleft-h'and laminae each havinga.

lateral projection extending outwardly there ty dogs for stopping descent of the skip in' the T8 'event of an emergency; springs continually urg- .:ing'the safety dogs intozpositionfor stopping descentofithe skip, and-a' -mechanical connection betweensaidspringsand the drawbar preventing the/springs fr'orn'moving the safety dogs into said-stopping positionso long as the drawbar is held. at itsxupper' limitof movement relative to the yoke butpermitti'ng, the springs to move the safetytdogsinto said stopping position when the drawbar'is not soheld.

:7.1The combination with a hoist skip'having, a yoke by which it isisusp'ended from a cable, of a drawfbar according to claim 5 connecting the cable .to theryoke, safety dogs which when, in. an advanced position; prevent descentof the skip and when in .a retracted position permit. descent thereof, springs urging the safety dogs into the advanced position, and levers for holding the "dogsin-the retracted position against the force ofv the springs; the. levers being mechanically connected to theflateral projections of the drawbar laminae so that the safety dogs are held thereby in their retracted position when the drawbar is-at its upper limit of movement relative-to the yokebut are released to be moved by 'thesprings to their advanced position when the drawb'ar is at its lower limit of'movement'rela- 'tive to the yoke. I

CLIFFORD D. WOODWARD.

' MARCUS MCCANNA.

REFERENCES GI'I'ED The following references are of record in th filje of 'tl iis patent:-

, v UNITED STATES PATENTS 21403333 Bjerke June 2, 1948 .5 wire rope 39- to the drawbar. One end of each of these lengths of wire rope is anchored by a pin to the segmental pulley with which it engages,

and the other end is secured to a laterally extending projection 4| formed integrally with one or more of the right-hand and one or more of the left-hand laminae HR and UL. In the drawbar shown in-the drawings, only one centrally assembled right-hand lamina and one centrally assembled left-hand lamina is :formed' with a lateral projection 4| of this character, positioned about at the junction between the central portion I9 and the upper portion 20 of the lamina of which it is apart. Each of these lateral projections 4| is apertured to form an eyelet in which the upper end of the wire rope 39 attached thereto is anchored.

The lengths of the wire ropes 39 are such that when the drawbar is held up with its solid base in contact with the bottom surface of the yoke (th position shown in Figs. 2 and 4), a force is transmitted through the ropes 39 and the lever arms of the segmental pulleys 38 and exerts a torque on the safety dog shafts, holding these shafts, against the opposite torque of the springs,

' in a position such that the safety dogs 34 are out i of engagement with the hoist guide rails l4. The

upward force exerted on the drawbar by the cable, opposing the force of gravity acting on the skip and its contents, normally holds the drawbar in the position shown in Figs. 2 and 4, in which position the safety dogs do not engage the guide rails-l4. Should the cable break, however, or if 'for any other reason the upward force transmitted through the drawbar to prevent free fall of the skip is released, then there is no longer sufiicient force acting in an upward direction on the drawbar to hold its base against the skip yoke .l5. In consequence, th torsion springs are enward movement of the drawbar relative to the yoke must be adequate to permit the required degree of rotation of the safety dog shafts while the drawbar remains connected through the ropes 39 to the segmental pulleys 33. The position of the drawbar and safety dogs, when the latter are in gripping engagement with the guide rails, is shown in Fig. 5.

The form of the safety dogs shown in the drawings and described above are, of course, for use in connection with skips operating on wooden guide rails, into which the teeth of the safety dogs can bite. In cases where steel or steel-faced guide rails are employed, the safety dogs are in the form of wedges by which a pair of steel jaws are caused to clamp on to the guide rails. Such wedge-type safety dogs can be operatively connected to the drawbar of the invention in essentially the same manner as described above. In any event, the particular form of the safety dogs is not a part of the present invention, but is, on the contrary, well known to the art. The present invention is directed, rather, to the design and construction of the drawbar itself and its direct connection to the safety-dog operating mechanism. In the foregoing description, the direct connection is by means of the wire ropes 39 and the segmental pulleys 38, but alternative designs '6 for effecting such connection through pivoted levers will be readily apparent to those skilled in the art, and are included within the scope of the invention.

We claim:

1. In a hoist comprising a skip movable vertically on vertical guide rails, said skip being provided with a transverse yoke by which it is suspended from a hoisting cable and having a pair of safety dog shafts horizontally mounted on opposite sides of the yoke, a' safety dog mounted on each shaft adjacent a guide rail, and spring means urging rotation of each shaft in a direction to cause gripping engagement of the safety dogs with the guide rails, the improved means for connecting the cable to the yoke and for normally preventing engagement of the safety dogs with the guide rails comprising a laminated drawbar'each lamina of which is in the form of 'a narrow elongated hook, the laminae being assembled alternately right-hand and left-hand j connected at one end to one of said lateral projections and at the other end through a lever arm to one of the safety dog shafts, the yoke slot in the drawbar being of greater vertical height than the yoke itself, and said ropes being of such length that when the drawbar is held up with its base in contact with the yoke they exert a torque on the shafts opposed to the spring means which prevents such rotation of said shafts as would bring the safety dogs into engagement with the guide rails but when the drawbar is not so held such torque is released.

2. A drawbar for a hoist comprising an assembly of laminae, each lamina being in the form of a narrow elongated hook, the laminae being arranged alternately right-hand and left-hand so that the assembled drawbar has a narrow transverse slot for receiving the yoke of the hoist skip, a solid base, a paled body, and a solid upper portion, said upper portion being configured to form an eyelet for attachment to a hoist cable, and said laminae being secured tightly together by transverse bolts extending through both the solid base and the solid upper portion.

3. A drawbar for a hoist assembled from a considerable number of laminae each of which is in the form of a narrow elongated hook, the laminae being arranged alternately right-hand and left-hand so that the drawbar has a transverse slot for receiving the yoke of the hoist skip, a solid base for supporting said yoke, a paled body, and a solid upper portion, a pair of bolts extending transversely through said solid base on opposite sides of the slot and a bolt extending transversely through said solid upper portion just above the slot for fastening said laminae securely together, and an eyelet bushing extending through said solid upper portion above said bolt therein.

4. A drawbar for connecting the yoke of a hoist skip to a cable, said drawbar comprising a considerable number of laminae each of which is in the form of a narrow elongated hook and which 

